I. Field
The present disclosure relates generally to communication, and more specifically to estimation techniques for wireless communication.
II. Background
In a wireless communication system, a transmitter typically processes (e.g., encodes and modulates) traffic data to generate data symbols. For a coherent system, the transmitter multiplexes pilot symbols with the data symbols, processes the multiplexed data and pilot symbols to generate a radio frequency (RF) signal, and transmits the RF signal via a wireless channel. The wireless channel distorts the transmitted RF signal with a channel response and further degrades the signal with noise and interference.
A receiver receives the transmitted RF signal and processes the received RF signal to obtain samples. For coherent data detection, the receiver estimates the response of the wireless channel based on the received pilot symbols and derives channel estimates. The receiver then performs data detection (e.g., equalization) on the samples with the channel estimates to obtain data symbol estimates, which are estimates of the data symbols sent by the transmitter. The receiver then processes (e.g., demodulates and decodes) the data symbol estimates to obtain decoded data.
The quality of the channel estimates may have a large impact on data detection performance and may affect the quality of the data symbol estimates as well as the reliability of the decoded data. Thus, it is desirable to derive high quality channel estimates. Channel estimation is challenging if the wireless channel conditions can change over time. For example, the wireless channel may be relatively static at one moment and rapidly changing at another moment, e.g., due to mobility of the transmitter and/or the receiver. A channel estimation scheme that can provide good channel estimates for certain channel conditions (e.g., a static channel) may not work well for other channel conditions (e.g., a rapidly changing channel).
There is therefore a need in the art for techniques to derive high quality channel estimates under different channel conditions.